lewm
said..."The driver stage is typically low stress, and, since there is no gain in
the driver stage, most likely to be "quiet". Try the "bad" tubes in the driver
stage and let us know what happens. What is the vintage and brand of the
original set of "stock" tubes?"
Lewm,I did just that,checking all of them through the drive stage. Four were noisy and two were quiet. I own a Prima Luna Dialogue Premium preamp purchased on 5/28/15. The preamp came with Primaluna stock tubes all around. They are all as quiet as a tomb... with roughly 600-700 hours on them. The NOS may have 125 hours of use.
Lewm,I did just that,checking all of them through the drive stage. Four were noisy and two were quiet. I own a Prima Luna Dialogue Premium preamp purchased on 5/28/15. The preamp came with Primaluna stock tubes all around. They are all as quiet as a tomb... with roughly 600-700 hours on them. The NOS may have 125 hours of use.